appliesResult to StratifierResult in detailed results output

src/calculation/DetailedResultsBuilder.ts

@@ -304,10 +304,27 @@ export function createPatientPopulationValues(
     populationGroup.stratifier.forEach(strata => {
       if (strata.criteria?.expression) {
         const value = patientResults[strata.criteria?.expression];
+
+        // if the cqfm-appliesTo extension is present, then we want to consider the result of that
+        // population in our stratifier result
+        const appliesToExtension = strata.extension?.find(
+          e => e.url === 'http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-appliesTo'
+        );
+
+        let popValue = true;
+        if (appliesToExtension) {
+          const popCode = appliesToExtension.valueCodeableConcept?.coding?.[0].code;
+          if (popCode) {
+            popValue = patientResults[popCode];
+          }
+        }
         const result = isStatementValueTruthy(value);
+        const appliesResult = isStatementValueTruthy(value && popValue);
+
         stratifierResults?.push({
           strataCode: strata.code?.text ?? strata.id ?? `strata-${strataIndex++}`,
           result,
+          appliesResult,
           ...(strata.id ? { strataId: strata.id } : {})
         });
       }

src/types/Calculator.ts

@@ -231,6 +231,12 @@ export interface StratifierResult {
    * True if patient or episode is in stratifier. False if not.
    */
   result: boolean;
+  /**
+   * True if patient or episode is in stratifier AND the population
+   * result it appliesTo is true. False if not. Only implemented for
+   * patient based measures currently.
+   */
+  appliesResult?: boolean;
   strataId?: string;
 }
 

test/unit/DetailedResultsBuilder.test.ts

@@ -1111,6 +1111,102 @@ describe('DetailedResultsBuilder', () => {
     });
   });
 
+  describe('Patient Population Values', () => {
+    test('should take population result into consideration when appliesTo extension exists', () => {
+      const populationGroup: fhir4.MeasureGroup = {
+        stratifier: [
+          {
+            id: 'example-strata-id',
+            extension: [
+              {
+                url: 'http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-appliesTo',
+                valueCodeableConcept: {
+                  coding: [
+                    {
+                      system: 'http://terminology.hl7.org/CodeSystem/measure-population',
+                      code: 'initial-population',
+                      display: 'Initial Population'
+                    }
+                  ]
+                }
+              }
+            ],
+            criteria: {
+              expression: 'strat1',
+              language: 'text/cql'
+            }
+          }
+        ]
+      };
+
+      const patientResults: StatementResults = {
+        'Initial Population': false,
+        Denominator: false,
+        'Denominator Exclusion': false,
+        Numerator: false,
+        'Numerator Exclusion': false,
+        strat1: true
+      };
+
+      const { stratifierResults } = DetailedResultsBuilder.createPatientPopulationValues(
+        populationGroup,
+        patientResults
+      );
+
+      expect(stratifierResults).toBeDefined();
+      expect(stratifierResults).toHaveLength(1);
+      expect(stratifierResults).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({
+            strataId: 'example-strata-id',
+            result: true,
+            appliesResult: false
+          })
+        ])
+      );
+    });
+
+    test('does not take any population result into consideration when appliesTo extension does not exist', () => {
+      const populationGroupNoExtension: fhir4.MeasureGroup = {
+        stratifier: [
+          {
+            id: 'example-strata-id-2',
+            criteria: {
+              expression: 'strat2',
+              language: 'text/cql'
+            }
+          }
+        ]
+      };
+
+      const patientResults: StatementResults = {
+        'Initial Population': false,
+        Denominator: false,
+        'Denominator Exclusion': false,
+        Numerator: false,
+        'Numerator Exclusion': false,
+        strat2: true
+      };
+
+      const { stratifierResults } = DetailedResultsBuilder.createPatientPopulationValues(
+        populationGroupNoExtension,
+        patientResults
+      );
+
+      expect(stratifierResults).toBeDefined();
+      expect(stratifierResults).toHaveLength(1);
+      expect(stratifierResults).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({
+            strataId: 'example-strata-id-2',
+            result: true,
+            appliesResult: true
+          })
+        ])
+      );
+    });
+  });
+
   describe('ELM JSON Function', () => {
     test('should properly generate episode-based ELM JSON given name and parameter', () => {
       const exampleFunctionName = 'exampleFunction';